5.1 evidence for evolution Flashcards
evolution
the cumulative change in the heritable characteristics of a population
3 evidences for evolution
fossil record, selective breeding, homologous structures
transitional fossils
demonstrate the intermediary forms that occurred over the evolutionary pathway taken by a single genus
example of a transitional specie
archaeopteryx
(transition to from dinosaurs to birds)
how does the fossil record show evolution?
Fossils can be dated by determining the age of the rock layer (strata) in which the fossil is found.
Sedimentary rock layers develop in a chronological order, such that lower layers are older and newer strata form on top.
law of fossil succession
chronological sequence of complexity by which characteristics appear to develop. This ordered succession of fossils suggests that newer species likely evolved as a result of changes to ancestral species
fossil sequence of animal phyla (7)
shelled invertebrates, fish, amphibians, reptiles, mammals, birds, man
fossil sequence of plant phyla
algae, bryophytes, filicinophytes, gymnosperms, angiosperms
how do transitional fossils show evolution?
They establish the links between species by exhibiting traits common to both an ancestor and its predicted descendents
selective breeding
a form of artificial selection, whereby man intervenes in the breeding of species to produce desired traits in offspring
how does selective breeding prove evolution?
targeted breeds can show significant variation in a (relatively) short period
examples of selective breeding (domesticated animals)
horses, cows, dogs
how do homologous structures prove evolution?
Comparative anatomy of groups of organisms may show certain structural features that are similar, implying common ancestry
homologous structures
Anatomical features that are similar in basic structure but have different functions
adaptive radiation
whereby several new species rapidly diversify from an ancestral source, with each new species adapted to utilise a specific unoccupied niche
example of homologous structure
pentadactyl limb
how has the pentadactyl limb adapted for different species?
- Human hands are adapted for tool manipulation (power vs precision grip)
- Bird and bat wings are adapted for flying
- Horse hooves are adapted for galloping
- Whale and dolphin fins are adapted for swimming
convergent evolution
when species have different origins but have become similar bc they perform the same or similar function
vestigial organs
reduced structures that serve no function anymore (ex: appendix)
- Changes to the environment have rendered these organs redundant and so over time they have lost their functionality
speciation
populations of a species can gradually diverge into separate species by evolution
how does speciation work?
- 2 populations of a species separate & do not interbreed
- the two populations will adapt to the different environmental conditions and gradually diverge from one another
- the longer they’re apart, the more variation (divergence)
- at a certain point they can no longer interbreed, and are therefore 2 separate species
analogous structures
features of diff. species that are similar in function but not necessarily in structure, and do not have a common ancestor
examples of analogous structures
wings of birds and butterflies, flippers of penguins and dolphins, eyes of octopus and mammals, sweet potato and potato
allopatric speciation
a species population becomes separated by a geographic barrier, whereby reproductive isolation evolves producing two separate species
continuous variation
a type of variation that is controlled by many genes, has a wide range of variability and is easily influenced by the environment
